Recycling arrangement for retarding plug formation in a shutdown slurry pipeline

ABSTRACT

Method and apparatus for retarding plug formation in a shutdown slurry pipeline. Means is provided whereby slurry liquid phase within upper elevations of the shutdown line is recycled into lower portions of the line where slumping and compacting of the solid phase may occur.

United States Patent Inventor Paul E. Titus Houston, Tex.

Appl. No. 802,617

Filed Feb. 26, 1969 Patented July 6, 1971 Assignee Shell Oil Company NewYork, N.Y.

RECYCLING ARRANGEMENT FORRETARDING PLUG FORMATION [N A SHUTDOWN SLURRYPIPELINE 4 5 Claims, 2 Drawing Figs.

US. Cl 302/14, 302/64, 302/66 int. Cl 865g 53/30 FieldoiSearch 302/14,15, i6, 64, 66

[56] References Cited UNITED STATES PATENTS 562,232 6/! 896 Miller1,329,967 2/1920 Greenstreet.... 2,093,970 9/1937 Longnecker 3,038,7606/l962 Crooke Primary Examiner-Andres H. Nielsen Attorney'sThomas R.Lampe and J, H. McCarthy ABSTRACT: Method and apparatus for retardingplug formation in a shutdown slurry pipeline. Means is provided wherebyslurry liquid phase within upper elevations of the shutdown line isrecycled into lower portions of the line where slumping and compactingof the solid phase may occur.

PATENTEUJUL Si n 3,591, 239

INVENTOR.

P. E TITUS BY/Z HIS ATTORNEY RECYCLING ARRANGEMENT FOR RETARDING PLUGFORMATION IN A SIIU'IDOWN SLURRY PIPELINE The present invention relatesto pipeline transport operations and, more particularly, to a method andapparatus for retarding plug formation by slurry solid-phase material ina pipeline during a shutdown period.

Transportation by pipeline is a major and growing industry. With the usethereof formerly confined almost entirely to movement of water, gas andpetroleum products, pipelines, with the advent of slurry transport, havebecome useful for long and short hauls of a wide variety of rawmaterials and finished products.

With respect to the pipelinetransportation of materials in slurry form,problems arise when such materials are moved through pipelines inclinedto go over ahill or down into a val ley. At these locations, during aplanned or emergency line shutdown, the solids of the transported slurrymay settle out vertically and subsequently slide down the inclinedportions of the pipeline, thereby causing a compacted plug which may bevery difficult to dislodge and move when line shutdown is ter' minatedand transport activities are resumed.

These difficulties are most commonly avoided by laying solids-carryingor slurry pipelines so that they do not exceed a slope or angle ofinclination below which sliding does not occur. Alternatively, theinclined pipeline sections are emptied at each shutdown. Obviously,these alternative prior art approaches are not always feasible oreconomical, especially in those situations where long and relativelysteep slopes are encountered. Slopes of this nature are beingencountered with increasing frequency as pipeline operations are beingextended to new relatively inaccessible mountainous areas in the UnitedStates and elsewhere.

SUMMARY OF THE INVENTlON It is therefore a primary object of the presentinvention to provide an improved and economical apparatus and methodwhereby slurry solid-phase material being transported in an inclinedpipeline section is prevented from forming a tightly compacted plugduring a line shutdown.

This and other objects have been attainedin the present invention byproviding a method and apparatus for retarding plug formation in ashutdown slurry pipeline wherein a conduit is operatively associatedwith the line so as to provide communication between upper elevations ofthe line and lower segments of the line with the conduit having pumpmeans disposed therein. The pump means is actuated when the pipelineflow rate falls below some predetermined level to pump liquid-richslurry material from the line upper elevations to lower points in theline. In this manner, slurry solid-phase materials slumping within theline are continually agitated so as to prevent formation of a compactedplug under the influence of gravity.

DESCRIPTION OF THE DRAWING The above-noted and other objects of thepresent invention will be understood from the following description,taken with reference to the accompanying drawing. In describing theinvention in detail, reference will be made to the drawing in which likereference numerals designate corresponding parts throughout severalviews in which:

FIG. 1 is a diagrammatic view illustrating a given length of slurrypipeline which has been modified in accordance with the teachings of thepresent invention; and

FIG. 2 is an enlarged diagrammatic cross-sectional view in longitudinalprojection illustrating an inclined portion of the pipeline section ofFIG. 1 with a conduit and pump means in operative association therewithin accordance with the teachings of the present invention.

Referring now to FIG. l, a given length of slurry pipeline I1 isillustrated in the position assumed thereby as the pipeline proceeds toand from a valley formed between two bills or mountains l2 and 13. Theterrain illustrated is typical of that encountered in pipeline-layingactivities, although it should be understood that the teachings of thepresent invention may be carried out in any topographical configurationwherein a portion of slurry pipeline is inclined.

The transportation of slurries consisting of solid particles in a fluidmedium by use of pipelines similar to that disclosed in FIG. 1 is quitewell known, and such expedient is finding increasing use, especially inthose situations where the source of raw materials is relatively remoteand inaccessible from the point of delivery, which may be a suitableprocessing plant, for example. In the disclosed arrangement, it may beassumed for purposes of illustration that the slurry material beingtrans ferred through pipeline II as by means of conventional pumps (notshown) is moving through the line in the direction indicated by thearrows. However, the teachings of the present invention are, of course,applicable regardless of the direction of flow ofthe slurry.

As long as flow continues in the pipeline, the solid matter of theslurry will remain in suspension within the pumped liquid, even when thesolid matter has a higher specific gravity than the liquid. If, however,the flow is stopped for any reason, i.e., the pipeline is shut down,such solid matter will settle out of suspension. In the situation wherethe line is horizontal or the slope of the line is insufficient to causesliding of the settled solids, no problem is created by such settlingout. Under these conditions, a liquid-rich channel remains open at thetop of the line which allows the settled material to be resuspended witha minimum of difiiculty upon resumption of slurry flow.

A serious problem can exist when the pipeline must be inclined to goover a hill or down a valley, as illustrated, for example, in FIG. I. Atthese locations, the settling of solids followed by their sliding downthe slope during a protracted shut down can result in a compacted plugof material difficult, if not impossible, to move or resuspend. In theillustrated pipeline configuration, such solids would slide downwardlyinto the valley formed between hills or mountains l2 and 13. The solidmaterial would then compress under its own weight to form a plug in thevalley in an obvious manner.

Such plug formation is retarded in accordance with the teachings of thepresent invention as follows. In FIG. 1 a conduit I4 is illustrated asbeing in operative association with pipeline 11 with the conduitproceeding from an upper elevation of the line, i.e., that portion ofthe line disposed on hill 12, to a lower portion of the line positionedin the valley lying between hills 12 and 13. A pump 15 is. disposed at aselected location along conduit 14.

As described above, upon termination of slurry flow the slurrysolid-phase material tends to settle or slump within the line. Suchaction results in the formation of a liquid-rich slurry mixture in theupper elevations of the line. Plug formation is retarded in accordancewith the teachings of the present invention by actuating pump 15 whenthe slurry flow rate has terminated or fallen below some predeterminedlevel. The pump serves to transport the liquid-rich slurry mixture downconduit 14 whereupon the mixture is introduced into the lower portionsof the pipeline 1]. The introduction of the liquid-rich slurry mixturemaintains the slumping slurry solid phase in continuous agitation withthe result that a solidphase-liquid-phase slurry mixture is maintainedwith compacting and plug formation by the slurry solid-phase materialbeing prevented. Upon pipeline restart, pump 15 is shut down and theslurry within pipeline 11 may be readily transported.

Conduit 14, rather than being connected at one downhill point of thepipeline, as diagrammatically illustrated in FIG. I, may be connected tothe pipeline at a plurality of downhill locations. In FIG. 2, forexample, conduit 14 is illustrated as being connected between an upperelevation of the line and a plurality of downhill pipeline locationsthrough manifold pipes 21-24. Valve members 31-34 are operativelyassociated with the manifold pipes and by maintaining all four valves inan open condition the liquid-rich slurry mixture being conveyed thrpughconduit 14 by means of pump 15 may be introduced at a plurality ofpipeline locations to provide a degree of slurry agitation within theline not possible with a single pipeline inlet. Still additionalpipeline inlets may be provided by branching each manifold pipe so thatit enters into the pipeline at a plurality of locations. With respect tomanifold 24, for example, a plurality of manifold subs ll- 33 extendtherefrom to the pipeline.

I claim as my invention:

1. Apparatus for selectively retarding and dissipating a plug caused bythe slumping and compacting of slurry solid-phase material in a shutdownpipeline utilized to transport a slurry fluid comprising a solid phaseand a liquid phase, said pipeline having at least one portion thereofinclined to the horizontal and at least a lowermost portion in fluidcommunication with said inclined portion where plug formation is likelyto occur due to slumping and compacting of said solid phase under theinfluence of gravity when pipeline flow has terminated, said apparatuscomprising:

means defining a flow path externally of said pipeline between saidinclined portion of said pipeline and said lowermost portion of saidpipeline; and

pump means operatively associated with said means defining a flow pathexternally of said pipeline to pump slurry fluid from the inclinedportion of the pipeline to the lowermost portion of the pipeline toagitate said slurry solid phase and maintain said solid phase insuspension with said liquid phase at said lowermost portion.

2. The apparatus according to claim 1 wherein said means defining a flowpath externally of said pipeline includes a conduit in communicationwith the interior of said pipeline at at least two locations along saidpipeline.

3. The apparatus according to claim 2 wherein manifold means isoperatively associated with said conduit and said pipeline whereby saidslurry fluid may be pumped into said pipeline at a plurality oflocations along said lowermost portron.

4. A method of selectively retarding and dissipating a plug caused bythe slumping and compacting of slurry solid-phase material in a shutdownpipeline utilized to transport a slurry fluid comprising a solid phaseand a liquid phase, said pipeline having at least one portion thereofinclined to the horizontal and at least a lowermost portion in fluidcommunication with said inclined portion where plug formation is likelyto occur due to slumping and compacting of said solid phase under theinfluence of gravity when pipeline flow has terminated, said methodcomprising:

establishing a flow path externally of said pipeline between saidinclined portion of said pipeline and said lowermost portion of saidpipeline; and

pumping slurry fluid from the portion of the pipeline lying along saidinclined portion along said flow path whereby said slurry fluid isinjected into the pipeline at the lowermost portion of the pipelinewhereby said slurry solid phase is agitated and maintained in suspensionwith said liquid phase at said lowermost portion.

5. The method according to claim 4 wherein said slurry mixture isinjected into the pipeline at a plurality of locations along the portionof the pipeline lying along said lower elevatron.

1. Apparatus for selectively retarding and dissipating a plug caused bythe slumping and compacting of slurry solid-phase material in a shutdownpipeline utilized to transport a slurry fluid comprising a solid phaseand a liquid phase, said pipeline having at least one portion thereofinclined to the horizontal and at least a lowermost portion in fluidcommunication with said inclined portion where plug formation is likelyto occur due to slumping and compacting of said solid phase under theinfluence of gravity when pipeline flow has terminated, said apparatuscomprising: means defining a flow path externally of said pipelinebetween said inclined portion of said pipeline and said lowermostportion of said pipeline; and pump means operatively associated withsaid means defining a flow path externally of said pipeline to pumpslurry fluid from the inclined portion of the pipeline to the lowermostportion of the pipeline to agitate said slurry solid phase and maintainsaid solid phase in suspension with said liquid phase at said lowermostportion.
 2. The apparatus according to claim 1 wherein said meansdefining a flow path externally of said pipeline includes a conduit incommunication with the interior of said pipeline at at least twolocations along said pipeline.
 3. The apparatus according to claim 2wherein manifold means is operatively associated with said conduit andsaid pipeline whereby said slurry fluid may be pumped into said pipelineat a plurality of locations along said lowermost portion.
 4. A method ofselectively retarding and dissipating a plug caused by the slumping andcompacting of slurry solid-phase material in a shutdown pipelineutilized to transport a slurry fluid comprising a solid phase and aliquid phase, said pipeline having at least one portion thereof inclinedto the horizontal and at least a lowermost portion in fluidcommunication with said inclined portion where plug formation is likelyto occur due to slumping and compacting of said solid phase under theinfluence of gravity when pipeline flow has terminated, said methodcomprising: establishing a flow path externally of said pipeline betweensaid inclined portion of said pipeline and said lowermost portion ofsaid pipeline; and pumping slurry fluid from the portion of the pipelinelying along said inclined portion along said flow path whereby saidslurry fluid is injected into the pipeline at the lowermost portion ofthe pipeline whereby said slurry solid phase is agitated and maintainedin suspension with said Liquid phase at said lowermost portion.
 5. Themethod according to claim 4 wherein said slurry mixture is injected intothe pipeline at a plurality of locations along the portion of thepipeline lying along said lower elevation.